Given the author's advanced age, weight, interest in other projects and slow writing style you might be waiting a while. He did tell the HBO creators the general outline of how he currently sees the story ending in case he passes on or the show catches up to the books.
I'm not sure why the last time I checked "A wiki of ice and fire" I was under the impression that only one book is left. Goodness gracious, there's a 7th book left and with no end in sight for the 6th. Back to plans for water-boarding Martin.
"Fire cannot kill a dragon." -Daenerys Targaryen, Game of Thrones
He did tell the HBO creators the general outline of how he currently sees the story ending in case he passes on or the show catches up to the books. 
Back to plans for water-boarding Martin. 
